Sinking of caissons and the building of piers, etc.



lJ. S. MILLER Feb. 28, 1933.

SINKING 0F CAISSONS AND THE BUILDING OF` PIERS, ETC

Filed June 10, 1932 INVENTOR J. S. MILLER Feb. 28, 1933.`

SINKING or'I cAIssoNs AND THE BUILDING oF PIERsI ETC 2 Sheets-Sheet Filed June l0 1932 EL-l'lO Paitenxedieb. 2s, 1933 UNITED *STATESY wxralw'r` OFFICE JAMES SMITH MILLER', 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO THE BRAVO CONTRACTING COMPANY, A. CORPORATION F PENNSYLVANIA SINKING OIE'` UISSONIS .AND THE BUILDING- OF PIERS, ETC.

Application led June 10,

This invention relates to, the sinking of Caissons and the building of pier-bases, and such like structures, and consists in improvements in caisson structure and in the method 5 of sinking, in consequence of which. the work may be carried to greater depth than .otherwise would be possible and may go forward with greater safety and may be accomplished with saving of material.

The invention is illustrated in the accompanying drawings. Fig. I is a view in vertical section ofthe caisson as it is ioated to place, before the sinln'ng is begun; Fi .l Il is a view on the same plane of section o the caisson sunk to its ultimate position and of the pier-base, theubuilding of which is ac-l complished in the sinking of the caisson; and

Fig. III is a view in horizontal section, and

on four planes ofsection, of the structure of 2Q Fig. II. The planes of section are indicated by the legends which the drawings bear.

In the particular case chosen for purposes n oi illustration, the caisson is to be sunk in the bed of a streamk to a depth of 170 feet below the level of low water. The depth of the wa-v ter at that'peint is from 60 to 90 feet; and,

accordingly the caisson is to be sunk from 80 to 110 feet in the bottom of the streanf.

Y The bottom is, to the depth of the work, com` Y posed wholly of a d posit yof sand and silt.

The pneumatic mthod of excavation: the

` kmethod, that iste say, of filling the bell .of

Ithe c`aisson"witl 1 compressed aiir, andin so doing driving .waterV from the space within .35 the bell and admitting workmen through the dredging wells to excavate the earth beneath the bell, is a method which is not'prac- `ticable beyond the point at which ahead of water greater than 110 to 120 feet obtains. 40 In this instance, therefore, the sinking of the caisson must necessarily be completed by dredging; and, as a matter of fact, with the qualification presently to be described, will advantageouslyv be performed wholly by dredging.

Referring first to Fig. I, the caisson includes' a bell, a coifer wall, and dredging wells. rI`he bell, in the form of an inverted Span of oblong shape, consists of a rim 1 and 50 a vfloor 2. From the rim of thebell rise the abovethe waterflevd,I and always as they are' 1932. serial No. 616,452.

vertical and water-tight col'er walls :Lia-nd,

surrounding orices in the floor of the bell, M rise the dredging wells 4. The bell is formed of steel plate; its rim is reenforced with concrete filling a steel-braced shell. The coer y wall to the height of 26 feet from the vrim of the bell is formed of steel plate; from that point upward it is `formed of timber; and, throughout all its extent, all seams .are properly caulked or otherwise made watertight. The orifices in the ioor of the bell and the dredging wells which rise from them are advantageously circular, and in this case are 10 to 12 feet in diameter. `The Walls of the well are made of, steel plate and all ,seams mi4 are water-tight. The caisson consistin of thek partsv described,A and illustrated 1n Fig. I, is floated to osition, and when brought to position is weighted' by the buildingin of masonry (orl0 dinarily in the form of concrete) on the upf per face of the -floorl of the ell and between the dred ing wells, at thev point'A, Fig. II.l rPhis -bui t-in -masonry becomes part of the substance of the pier-base itself, and the building-in progresses gradually as the caisson descends, until, ultimately, the pier-base p is completedin situ.k s a j The initial,` filling-in, continues y ntil the floating caissonis sunk and restsa the rim 30 4of the bell upon the bottom of the river. The

coifer walls and the walls lof the dredging wells are as a matter ofpractical convenf ience built up dually as .the caissn descends. lInitialyli:l they are of. suicient 35- height tofrise above the surface of the water when the caisson first is sunk and comes to rest on the bottom; and their gradual upward building maintains them always rising extended they are inade water-tight. When the caion has been brou ht to position and sunk, and rests upon the ottom of the stream, excavation begins. The riverbed material is cut from beneath the bell and removed through the dredging wells; and as the underlying material is so cut away and removed, thecaisson with itsgrowing burden of .masonry (or concrete) descends by gravity. A 1

The excavation and removal of the material will be accomplished in suon manner as circumstances dictate. To a depth of 110 feet or more below water-level it is practicable to send laborers into the space beneath the bell (the space being filled with compressed air) and by their aid to dig away the river-bed material. Necessarily, at greater depths (and, if the nature of the bed material be suitable, it may at higher levels be found advantageous and economical so to do) the material is removed by dredging. In such case compressed air is not used; wa- (er rises in the dredging wells to common level with the stream outside of coffer wall 3, and dredging buckets are lowered and raised through the wells 4 to and from the surface of the excavation beneath the bell.

If, in the progress of work, and at a depth not too great to forbid, such an obstacle as the trunk of a tree be encountered, lying in the sedimentary material of the river bed, that dredging well or those dredging wells beneath which the tree trunk lies may be sealed; air may be pumped in, water expelled from beneath the bell, and workmen may be sent in to remove the obstruction. If such an obstacle be met at greater depth, removal will be effected by means such as are ordinarily ado ted.

onsideration of Fig. III will make plain to those acquainted with the subject that the caisson here illustrated ,is provided with an extraordinarily large number of excavating wells, and that the arrangement of the wells is remarkable, in thatv they are widely extended in their location, and that as many as possible are symmetrically arranged as near as possible to the outer margins of the bell. Such an arrangement makes possible the enjoyment of the invention of Letters Patent, No. 1,7 06,246, granted on my application, March 19, 1929. The arrangement makes ,possible the enjoyment to the fullest extent of a feature of invention in method.

In the progress of such work 1t not infrequently happens that the deposit through which the calsson is being sunk is in different portions unequal in the resistance it offers to the descent of the caisson, and that in consequence tendencies develop to effect a de! parture of the caisson from its desired path of vertical descent. Having such a caisson as has been described, I have perceived that I may correct such tendencies by sealing one or more of the wells on the side of the caisson toward which the caisson tends to tip and pumping in air. In so doing the column of water within the well is displaced downwardly, and a buoyant tendency 1s at that point set up. Meanwhile, on the opposite vside of the caisson, excavation may go forward, or the burden of masonry (or concrete) increased, until the tendency is over- In fuller explanatlon of tendenciesof the descending caisson to depart from its desired vertical path, there may be a tendency of the caisson to tip-a tendency of one of the opposite sides to descend more rapidly than the other-; or there may be a tendency to drift laterally from the intended path of descent; or, again, such particular tendencies .may `be simultaneously manifest. And under any such situation, the possibility exists of sealing particular ones of the plurality of diversely situated wells and `pumping in air, while continuing excavation through other particular wells. In such manner the descending caisson may be kept in its intended path.

. My further invention also has to do with maintenance of stability, and the prevention of damage and loss consequent upon the tippin of the growing pier-base from its inten ed vertical position. In the erection of such pier-bases it is usual to form, in the manner described, the foundation block or footing as a column of uniform cross-section from the bottom upward. I have discovered that by stepping-in, by reducing the crosssection of the growing pier-base in a plurality of steps at successive points, it is possible, not merely to save material without loss of strength; but it is possible also to maintain at lower level the center of gravity of the growing structure, and by virtue of that fact to make it more stable and more efectively to prevent tipping. Such successive steppingin will be noted, in Fig. II, at the points B (126 feet below water level), C (87 feet below water level), and D (35 feet below water level). It willv be perceived that by such stepping-in, not only may material be saved, but that structure may be brou ht to relatively close approximation to t e ideal in which with perfect economy of material the shape of maximum strength is attained.

Fig. II illustrates diagrammatically the -inished structure. The body of masonry (o1l concrete), the building of which begins at A as described, progresses as the caisson descends, with stepping-in as described, until the whole body is built. Always, until thel caisson approaches its ultimate position, the

building of the masonry or concrete is carextent, for added weight whichl does not afford increase of strength or security is not desired. l

I have indicated that, until the descending 5 caisson approaches its ultimate position, the masonry work is done below water-level. And from what has gone before it will be understood that, in orderwto build masonry below water-level, it is necessary to maintain the* height of the cofer wall above waterlevel. It remains to say that the point in the progress of theI operation at which the upward extension of the cofer wall may be in-l termitted is a point that will vary according 15 to the circumstances. 2

The invention has, a characteristic of great value: the capacity,namely, consequent upon building below'water-level, of maintaining the centerof gravity at a low point. Underk particular circumstances-in particular installations-that capacity, valuable initially,

.l may become less valuable and may cease to have any practical value as the caisson descends. That is to say, the deposit into which the caisson is sunk may be of such firmness that, as sinking progresses, liability of the growing structure to overturn ceases to signify; and in suchrlcase, when the sinking has vbeen carried to the point of security, the masonry may be-built up to a level\ above water-level, and from that stageA in the progress to the end the further upward extension of the coffenwall, being unnecessary, is dispensed with. The wallsgof the wells, howlever will be maintained always above'watereve I have described the vinvention as ,appliedin the erection of a pier-base in a river bed. Manifestly there islan incidental and non-y essential element in the circumstances; the essential characteristics lie in the erection of y a structure of masonry (or concrete) in a bed of water-flushed earth.

I claim as my invention:

1r. The method herein described of sinkin a caisson ground and to a depth below water-level exceeding the practicable limit of pneumatic excavation, which consists in bringing to position above its intended ultimate resting place a caisson including a bellV with water-tight floor a marginal water-tight coffer wall and a plurality of well with water-tight walls rising from orifices in its ioor, one at least ofsuch Wells being situated at a point remote from the center line of the bell but within the compass of the said coffer wall, building masonry upon the upper face of the floor of the bell and excavating through the wells tle underlying material, and in so doing causing thecaissonto sink while water rises in the wells, maintaining the height ofthe walls o f the wells always above Water-level, and in the progress bf sinkingV correcting tendencies of the caisson 05 to depart from a path of vertical descent by building masonry sealing and pumping air into a 'well remote i from the center line dif the bell and continumg the dredging through another of the wells.

2. The method herein described of sinking a caisson in ground and to a depth below kwater-level exceeding the practicable limit material, and in so-doing causing the caisson ,to sink while water rises in the dredging wells, maintaining the height of the coler wall and of the walls of the dredging wells always above water-level, and in theprogress of sinking correcting tendencies of the caisson to tip by sealing and'pumping air into a dredging well on the side which tends to sink lower.

3. VThe method herein described of establishing'a pier foundation in ground below water-level which consists in bringing to position above its intended Vultimate resting. place a caisson. including a bell with watertight floor marginal Water-tight coier wall and a plurality of dredging wells with watertight walls arising from orifices in the floor of the bell adjacent opposite mar ins but within the compassof thefs'aid co er wall, u on the upper -face of said bell within the cofiir wall and externally of the dredging wells, and dredging the underlying material` through the dredging wells, thus causing the structure to sink, maintaining 'the coffer wall and-the dredging-well walls at all times at a height exceeding .Waterlevel, and maintaining the sinking structure 110 in vertical descent in spitepf inequalities in resistance by confining in one dredging well a buoyant body of" air while continuing through another well the excavating oper-y ation.

4. The method herein described of building a pier in ground below water-level and from a depth below'water-level exceeding thev practicable limit 'of pneumatic excavating, which consists in bringing to` 120 position abdve its intendedl ultimate resting-place a caisson including a bell with water-tight ioor a marginal ,water-tightcoffer wall and a plurality OLdredgin/g wells with water-tight ,Walls' rising from ori- 125 ices in the Hoor of Athe bell situated adjacentopposite margins andwithin the compass of the cofer wall, building-a body of masonry-of upwardly diminishing cross-section upon the upper face of the floor of-the bell 130 within the coifer wall and externally of the dredging wells and at a level below the water-level outside, and excavating through the dredging wells the underlying material, and in so doing causing the structure to descend' by gravity, and in such descent correcting tendencies to tip by confining a buoyant body of air within a well on the side of the structure that tends to. sink faster than the other, and nally illing the space beneath vthe bell with concrete and building the aforesaid body of masonry to its ultimate intended height.

5. A caisson adapted to be sunk in ground below water-level including a bell with water-tight floor, a water-tight coiler wall rising marginally from the loor, and a plurality of water-tight dredging-well walls rising from orifices in the door arranged adjacent opposite margins of the bell and within the compass of the cofer wall, the space above the floor of the bell and -within the coifer wall and external of the dredging wells being accessible for thehbuilding-in of masonry as the caisson descends, the dredging wells severally adapted to stand open above and filled with columns of water to waterlevel or to receive and retain buoyant and water displacing volumes of compressed air.

In testimony whereof I have hereunto set my hand.

`JAMES SMITH MILLER. 

